General Info

With the development of genetic engineering, animal cell culture has produced a variety of highly effective drugs, sensitive diagnostic reagents and biotechnology products. At present, this direction is developing into a high-tech industry. Since animal cells are very different from microbial cells, there are strict requirements for in vitro culture. For example, animal cells are very sensitive to shear, and the design of the reactor cannot have as high shear force as microbial cells. Therefore, traditional microbial cell reactors should be modified to be suitable for animal bioreactors. It is very important and urgent to develop new bioreactors based on the characteristics of animal cells.

Introduction to animal cell culture:

Animal cell culture is a technology that removes cells from animals and disperses them into single cells to simulate the growth environment in the body. Under sterile, suitable temperature and rich nutrition conditions, cells continue to survive, grow, proliferate and maintain structure and function in vitro.

Animal cell culture process

In vitro culture can be divided into primary culture and subculture. Primary culture refers to the process of initial culture of cells removed from the body. Cultured cells that proliferate for about 10 generations are called primary cells; continued transfer culture from primary cultured cells is called subculture.

Types of in vitro culture of animal cells

(I) Suspension culture

Refers to the process of cells growing freely in suspension in a culture vessel. It is mainly used for non-adhesion-dependent cells. Such cells do not need to adhere to the wall for in vitro growth and can be suspended in culture medium using microbial methods.

Cells derived from blood and lymphatic tissues, many tumor cells (including hybridoma cells) and many recombinant cells belong to this type of cells. Because they grow in suspension, the cell density is generally high, which is easy to mass produce and process control.

(II) Adhesion culture

Refers to cell culture that must be attached to the surface of a solid medium for growth. It is mainly suitable for adhesion-dependent cells (also called adherent cells). Most animal cells belong to this type.

This type of cell growth needs to be attached to certain solid and semi-solid surfaces with an appropriate amount of positive charge. After the cells grow by attachment, they are no longer in their original form. The morphology is generally single, mainly fibroblastic, epithelial, migratory and polymorphic.

(III) Immobilized culture

This type of culture is suitable for both anchorage-dependent cells and non-anchorage-dependent cells, and has the advantages of high cell growth density, strong shear resistance and anti-pollution ability.

Due to the different cells cultured, the immobilized culture method is also different. Generally, collagen is usually used for anchorage-dependent cells, while calcium alginate is often used for non-anchorage-dependent cells. Commonly used cell immobilization methods include adsorption, covalent attachment, ionic/covalent crosslinking, embedding and microencapsulation.

Animal cell culture bioreactor

The large-scale culture of animal cells requires special reactors. Unlike microorganisms and plant cells, animal cells have no cell wall on the outer layer, the plasma membrane is brittle, and they are sensitive to shear and have strict requirements for the in vitro culture environment. Therefore, traditional microbial fermentation reactors cannot be used for large-scale culture of animal cells, and low shear effect, good transfer effect and mechanical properties are the principles that must be followed in the design or improvement of such reactors. Since the 1970s, bioreactors for cell culture have developed greatly, with more and more types and larger scales, but the main structural forms of reactors are still mainly stirring, airlift and fixed bed. In addition to cultivation for the purpose of artificial mutagenesis, the design principle of bioreactors for animal cell culture should be to simulate the growth environment of the culture in the organism as much as possible. Due to the particularity of animal cell growth, special attention should be paid to the design of the reactor structure and the selection of special carriers. The bioreactors for animal cell culture are roughly: airlift bioreactors, hollow fiber tube bioreactors, fluidized bed bioreactors, stirred tank bioreactors, stacked bed bioreactors, disposable bioreactors, membrane bioreactors, etc.

Two important animal cell culture fermenters:

 1. Stirred fermenter

Stirred fermenters rely on stirring paddles to provide stirring power. They have a large control range, good mixing and concentration uniformity, so they are widely used in biological reactions. Stirred fermenters in animal cell culture have all been improved, including improving the oxygen supply method, the form of stirring paddles, and adding accessories to the fermenter. The main difference between various animal cell culture stirred fermenters lies in the structure of the stirrer. The shapes of these stirrers are mainly rod-shaped, air blade-shaped, and cylindrical. The stirring methods mainly include surface stirring, deep stirring, and air flow stirring; the power source is magnetic or motor-driven.

2. Airlift fermenter 

Airlift fermenter is also one of the commonly used equipment for achieving high-density culture of animal cells, especially suitable for culturing shear-sensitive cells. Compared with stirred fermenters, airlift fermenters produce gentle and uniform turbulence, relatively small shear force, and no mechanical moving parts in the device, so the cell utilization rate is relatively low; direct injection of air to supply oxygen has a high oxygen transfer rate; large liquid circulation volume allows cells and nutrients to be evenly distributed in the culture medium.